Patience

May 13, 2021 George Wieber

This week, we’ll mix things up a bit. The topic is somewhat all-encompassing because we’ll be taking a look at time. By time, I mean timescales and how we as humans measure the strange phenomenon of time in units of “seconds”. What is a second anyways? Originally, the basis of the “second” was simply one day split into 86,400 equal parts, each of which was considered one second. One day was defined by the time it took for the Earth to rotate once on its axis, as determined by the position of the sun in the sky. This would be rather simple, except for the fact that the Earth’s rotation is slowing down slowly and is not always consistent… 400 million years ago, the Earth rotated on its axis 400 times (400 days) by the time it rotated around the sun once (one year). These days, we measure seconds on a much more consistent basis of the frequency of atomic radiation coming from a Cesium-133 atom transitioning between two hyperfine levels of ground state. Much more complicated, yes, but it seems to be working out alright. Regardless, the “second” still seems relatively short in our daily lives (except when you’re doing a plank). As arbitrary as one “second” is, we can use it to express one of the greatest enigmas known to mankind: time. This week, we’re going to explore the various timescales from the transient (femtoseconds) to the nearly infinite (exaseconds) and certain phenomena that occur over the various lengths of time. Hopefully this article doesn’t plunge you into an existential crisis… but that one’s on you.

See this content in the original post

We begin this journey at some of the shortest timespans humans have harnessed. It’s difficult to even conceptualize a femtosecond… light travels only about 0.3 micrometers over the span of a femtosecond. So it isn’t surprising that many of the things that occur within the timespan of a femtosecond or even a picosecond are usually extraordinarily tiny in scale. For example, the action of a single molecule vibrating and rotating occurs over the timescale of femtoseconds to picoseconds. It can even take a few hundred femtoseconds for two molecules to collide and react in a chemical reaction.

Perhaps something a bit easier to wrap our heads around is in the use of a femtosecond laser. Yes, laser pointers are fun to play with, but this type of laser is a bit different. What’s special about femtosecond lasers is that they shoot tiny bursts of light at a frequency of only a few hundred femtoseconds… so similar to if you could repeatedly press the button on a laser pointer for about 0.0000000000001 seconds each time in rapid succession. These special lasers are actually used in studying and visualizing molecular motions and transitions.

This shows the movement of an atom within a molecule over the span of hundreds of femtoseconds.

Outside of that, though, and perhaps more pertinent to our own lives, is the fact that femtosecond lasers are actually used in laser-assisted eye surgeries. LASIK eye surgery as well as surgery for cataracts both utilize a femtosecond laser to make tiny, precise incisions into the human eye.

Good thing we don’t use long-pulse microsecond lasers for eye surgery.

See this content in the original post

Yes, this is a joke, but it makes a point of showing that there are actually an incredible number of calculations computers perform during operations that last a few seconds.

Cycle speeds for everyday computers and the time to complete simple computer operations are typically measured on the scale of nanoseconds, although computers seem to continually get faster each year. The cycle speed measures how quickly a computer can carry out instructions or discrete operations, and this speed is measured in units of Hertz (Hz). If your computer operated at 1 Hz cycle speed, it would only be able to carry out one instruction per second (which is incredibly slow). Your typical computer might have something on the order of a few MegaHertz or GigaHertz for processing power, which means closer to 1,000,000,000 instructions processed per second. An alternative way to express these speeds is by stating that your computer processes each instruction in a single nanosecond. Now, an “instruction” can be pretty arbitrary to think about. One instruction would be something as simple as your computer adding 1+1=2. If you’re looking to play computer games, this requires MUCH more instructions to process; even simple division requires more than one “instruction”. Fortunately, nanoseconds are quite short, so something as complex as playing some tunes from your computer speakers while also working on a powerpoint presentation appears to be almost seamless (if your computer has enough processing power).

As we continue to reach longer spans of time, we get to the other end of this spectrum at microseconds. As an example, a lightning strike takes place over a couple hundred or thousand microseconds. A single bolt of lightning is made up of individual flashing “strokes” which each last about 30microseconds each. Since each bolt of lightning is made up of several rapidly flashing strokes, a full bolt of lightning as we see it actually ends up lasting somewhere from a few milliseconds to one second. The human eye actually can’t perceive any of the individual strokes of lightning in most cases since they exist on the scale of microseconds, so what we end up seeing as lightning is typically only the full bolt.

See this content in the original post

If you just want to see some slow-mo video of lightning, skip to 2:45 in the video.

See this content in the original post

Well, this realm of time is a bit easier to comprehend, but still quicker than you might think. The frame rate of the human eye is encompassed within this range of times, since your vision is not entirely continuous. Our brain processes the images from our eyes at a rate of about 30 to 75 frames per second. This is equivalent to a single image from our eyes being processed every 10 to 100 milliseconds. This is why we can’t perceive the fact that lightbulbs are actually continuously blinking. With the United States’ electrical infrastructure running at 60Hz (as alternating current), lightbulbs in your house blink at a rate of 120 times per second. Since this is much quicker than the human eye can perceive, we just end up seeing a continuous light coming from lightbulbs that are turned on.

Similarly, human reaction times are on the order of hundreds of milliseconds. The average reaction time to visual stimuli in college-age students has been calculated to be around 190 milliseconds, and reaction time to sound stimuli is around 160 milliseconds. Notice that reaction times are quicker for sounds as opposed to images (ears triumph over eyes). These reaction times are pretty quick… but not always quick enough. One study also showed that, on average, male participants had quicker reaction times than female participants, and those that regularly exercised had quicker reaction times than sedentary individuals.

Let’s slow things down even more to a few comfortable seconds. The human heartbeat at rest lasts about one second (if you’re healthy)! As short as one second or even one minute can be, there are plenty of things you can do in this span of time. Below is a sample of activities from the Guiness Book of World Records that were each performed in one minute…

74 pull-ups
25 marshmallows eaten
290 high-fives
13 ears of corn shucked
32 eggs cracked with one hand
87 hugs
18 costume changes

See this content in the original post

Also… when looking at the increase in his net wealth in recent years, Jeff Bezos earns close to $150,000 each minute.

How do you spend the minutes in your life?

See this content in the original post

This is where the base-10 system starts to get odd… who counts time in units of kiloseconds anyways? I’m sticking with it, though, for consistency. FYI, one kilosecond is about 16.7 minutes, and one Megasecond is approximately 11.6 days. So here we’re in the realm of one hour to a few years.

Cellular reproduction occurs at different rates in the human body, with some cells actually never getting replaced. Many of the human cells do replace themselves within the span of a few days to a few years. Some of the quickest turnover rates for cells in the human body occur over a few hundred kiloseconds - which is to say up to about 5 days. Your skin cells only last about 2 to 4 weeks, blood cells last a bit longer at around 4 months, and liver cells last around a few years (depending on use). Bone cells and the skeletal system renew about 10% of your skeleton each year. This process of renewing your body’s cells is continuous,

We can discuss some of the water cycle and weather over this timespan as well. A single molecule of water lasts about an average of 9 days in the atmosphere before falling back to Earth, usually as rain or snow, and seasons last a few months whether we’re talking a four-season year (Winter, Spring, Summer, Fall) or two-season year (Wet and Dry seasons). Water moving in the Mississippi River takes about 3 months to travel from its source in Lake Itasca to its destination in the Gulf of Mexico.

Meet Edward Payson Weston… one of the first recorded people to walk across the entire United States.

Speaking of traveling long distances, one of the first recorded instances of someone traversing the entire United States was in 1909 when a 70-year-old man named Edward Payson Weston walked across the country in just over one hundred days. Apparently this man was famous in the sport of competitive walking (also called “pedestrianism”). Since then, the record for fastest run across the United States was 42 days, six hours, and 30 minutes from San Francisco to New York.

When we get closer to the longer end of this spectrum - a few hundred Megaseconds (a few years) - we start to get into the timespan of typical business cycles. Business cycles take on an up-and-down motion with economic expansions followed by economic contractions (or recessions), similar to a wave. The length of time from one peak economic expansion to another peak economic expansion encompasses one entire business cycle. Since 1945 when WWII came to an end, there have been about 12 full business cycles in the United States. The average business cycle between years 1945-2020 has taken about 75 months to complete from one peak expansion to the next peak expansion. The same data from years 1945-2020 also shows that it takes an average of 11 months for peak economic expansion to reach the trough of the business cycle (basically it takes 11 months for the economy to fully crash). It then takes an average of 64 months from this economic low-point to reach the next peak economic expansion… before crashing again.

Business cycles in the United States since the end of World War 2.

See this content in the original post

Since we’re getting into some MASSIVE durations of time, I decided to take one step at a time here and stick with just Gigaseconds. Here’s where it gets weird. The human lifetime lasts only about 3 Gigaseconds - if you’re very healthy. Most humans do not even make it to 3 Gigaseconds which is about the same as 95 years. A number of animals live longer than humans, including Bowhead Whales which can last closer to 7 or 8 Gigaseconds. One deep-sea sponge (which is technically an animal) was estimated to be around 11,000 years old - which is close to 350 Gigaseconds. Besides lifetimes, though, what else can we measure in units of Gigaseconds?

We can measure the length of time it takes some substances - especially plastics - to decompose. Technically, plastics such as styrofoam or polyethylene used in plastic bags are broken down by sunlight such that tiny fragments are created instead of truly “decomposing”. Based on scientists’ estimates in this case, it may take around 500 to 1,000 years for certain plastics to “decompose”... optimistically. This would equate to around 16 to 32 Gigaseconds for these plastics to break down after being disposed. In landfills where the plastic is buried underground, there isn’t much opportunity for these plastics to break down, so some scientists have estimated that it could take over a million years for styrofoam in particular to decompose. One million years actually breaks our Gigaseconds scale and moves up to the next level, though we can still say that it would take over 30,000 Gigaseconds for the styrofoam to break down in the landfill.

The plastic from this styrofoam cup will likely be around long after you (and your grandchildren) die.

The timespan of entire human civilizations can also certainly be measured in Gigaseconds. If we consider both the Roman and Eastern Roman Empires as a single human civilization spanning approximately 1,500 years as one of the longest continuous human civilizations recorded, this would only be right around 47 Gigaseconds. The Great Pyramids at Giza, built around 2550 B.C. by the Ancient Egyptians, have been on Earth for about 144 Gigaseconds. Domestication of plants and animals for food and materials began around 10,000 years ago, which is around 315 Gigaseconds ago. Prior to that time, humans were hunter-gatherers.

See this content in the original post

As we continue along this journey through time, we reach the humble beginnings of humanity (as far as we hypothesize) at about 65 Teraseconds ago. Sixty five Teraseconds is equivalent to around 2 million years ago, and this is the approximate date attributed to evidence of the first “human-like” species emerging in Africa. The exact species that classifies humans, homo sapiens, didn’t actually emerge until 1,700,000 years later (about 9.5 Teraseconds ago). The entirety of humanity is now covered in Teraseconds, but we can discuss other things in Teraseconds, too, such as major geologic or climate shifts.

As much as we’re used to the polar ice caps being present on Earth, they haven’t always been there. The oldest ice frozen in Antarctica is estimated to be around 2.7 million years old, which is 85 Teraseconds. Jump back a bit further in time to 550 Teraseconds before today, and we reach a point when the average temperatures on Earth were too hot to sustain consistent polar ice caps. In 2021, we are now in what is considered an “interglacial”, meaning that we are between Ice Ages. Still, the temperatures on Earth today are rather cold when compared to historical temperatures that were unable to sustain polar ice caps (and even had a large number of animals and plants living comfortably at the north and south poles).

Deep ocean temperatures for the past 65 million years… we’re pretty cold today.

At this time 550 Teraseconds ago (close to 17 million years ago), the “Mediterranean Sea” was still dry and had not been filled with water. Many of the animals present on Earth were similar to those seen today. For example, horses, camels, deer, and dogs were all mammals alive at the time. The megalodon species was also alive and well in the ocean.

See this content in the original post

We FINALLY get to some dinosaurs when we talk about Petaseconds. Dinosaurs existed during the Mesozoic period, which ended about 65 million years ago with a mass extinction. The age of the dinosaurs first began 165 million years prior to THAT, so dinosaurs roamed the Earth for about a solid 6 Petaseconds, which is much more impressive than humans… we’re not even at one-tenth of a Petasecond yet for the entirety of our species.

Not to scale, but the pterodactyl is a cool addition.

Near the beginning of the Mesozoic era 250 million years ago, reptile-like creatures were better suited to the hot, arid environment. The temperatures were, on average, 30°F warmer than they are today. These temperatures declined over time (a VERY long time), though, and allowed the first mammals to emerge 230 million years ago.

While global temperatures during times like these are estimates, the science that goes into them is pretty interesting. One of the predominant ways of determining climate way back when is by using a ratio of oxygen isotopes. The Oxygen-16 isotope (present in water molecules and other compounds) is more prone to freezing at higher latitudes compared to the Oxygen-18 isotope during cold spells in Earth’s history. At the same time, the Oxygen-16 isotope returns to waters during warmer periods when the ice melts. By measuring the ratio of Oxygen-16 isotopes to Oxygen-18 isotopes in fossils and geologic layers with known ages, scientists can estimate what the temperatures and climate may have been during that period of time on Earth. Other aspects may also be thrown into this determination of past climate as well, such as finding fossilized palm branches at more northern latitudes suggests that the temperatures were once warmer than they are now.

This is almost as volatile as the stock market these days! Not really, though… it’s almost impossible to comprehend what 500 million years is like.

The scale of Petaseconds involves more than just dinosaurs and a different climate, though, and we reach all the way back to Pangaea 8 Petaseconds ago.

Movement of landmasses on Earth as part of the Continental Drift theory.

Pangaea was the supercontinent which is hypothesized based on our understanding of the Earth’s shifting tectonic plates. The massive landmass split apart and moved around over the span of these 8 Petaseconds to reach their current locations with the 7 continents we know and love today.

Even before this, though, was the beginnings of Earth as we know it about 140 Petaseconds ago based on current estimates. It was around this time that the Earth was simply a massive rock flying around the Sun colliding with other rocks. These collisions would likely have kept the Earth incredibly hot with molten rock on the surface. It was just before this that the Sun came into being due to collapsing gases that started nuclear fusion under the immense gravitational pull.

See this content in the original post

Whoops! We actually just reached the estimated lifespan of the universe as it exists now. That’s predicted at about 15 billion years, which is close to one-HALF of an Exasecond. Makes you wonder what was around before all of this…

Taking a moment to think about these timescales can sometimes help put our own lives into perspective. On one hand, we could be freaking out since our lives are so fleeting (hello, mid-life crisis); on the other hand, we can relax and recognize the opportunity held in every minute… or second… or nanosecond… ooooorrrrrrr femtosecond. Time doesn’t change (I’m ignoring the space-time relationship and related theories on this one, so bear with me), but our attitude towards time likely does change throughout our lives and even throughout the day, too. Perhaps a bit of reflection is in order… and maybe a bit of patience, too.

To think about…

Some studies suggest that time seems to move faster (days seem to grow shorter) as we get older. How has your perception of time changed throughout your life?
How accurate do you think are the estimates for what the Earth, or even the Universe, was like prior to recorded history?
Try to think of some other natural phenomena or other aspects of your life - which time scale would they fit into?

Sources

https://www.scientificamerican.com/article/from-instantaneous-to-eternal-2006-02/

https://www.ptb.de/cms/en/ptb/fachabteilungen/abt4/fb-44/ag-441/realisation-of-the-si-second/history-of-the-unit-of-time.html

https://www.bouldermedicalcenter.com/femtosecond-laser-cataract-surgery/

https://www.industrial-lasers.com/micromachining/article/16484884/femtosecond-laser-processing-of-metal-and-plastics-in-the-medical-device-industry

https://www.mpsd.mpg.de/17191/2015-12-ballet-miller

http://www.public.asu.edu/~gbadams/lightning/lightning.html

https://www.bbc.co.uk/bitesize/guides/zws8d2p/revision/2

http://ithare.com/infographics-operation-costs-in-cpu-clock-cycles/

https://usa.inquirer.net/64935/how-much-does-jeff-bezos-make-a-second

https://www.guinnessworldrecords.com/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4456887/