What is time?
If someone owns an auto repair shop, they probably receive panicked phone calls at odd hours from family and friends asking to fix a broken vehicle.
Similarly, doctors and lawyers are sometimes asked by family and friends for their advice on how to starve a cold and avoid a lawsuit, respectively.
Amazingly, the family astronomer receives all sorts of frenzied calls surrounding the big questions of our existence in the physical universe.
Yes, it is true and last Sunday I received a long, detailed list of questions from a beloved family friend who seemed upset. In this case, the family friend is the son of one of my father’s shipmates in World War II, aboard the USS Flasher. Flasher was a WWII submarine that sank more tons of enemy ships than any other submarine in history. Yes, our fathers were literally plankowners of the Greatest Generation (I still have some of the deck plank from the Flasher). The wood from Flasher’s deck is solid and strong like the generation it carried into battle.
By the time you finish reading this column, it shouldn’t bother your brain to hear time expressed as a function of distance; in other words, the term “Light Year” should make sense to you. In the “time” I spent at the U.S. Naval Observatory (USNO) in Washington, DC during the year 2006, I came to know and understand time much better than the average human being.
Dogs have a completely different understanding of time…they really don’t perceive time. In other words, if you leave your dog and return ten seconds later or ten weeks later your dog loves you all over again as if you never left because they have no sense of time.
Babies are the same way; time doesn’t really matter to them. I used to love playing this with our babies. I would use a stopwatch to see how long they could go and still be completely surprised by a Peek-a-boo. Whoa, where did the time go, I digress…
Time. We were discussing time, so we should settle on a definition of what time is. Time is a quantity that you measure with a clock. Our own U.S. Naval Observatory sports a pair of Hydrogen MASERs that serve the enire planet’s timekeeping system. One night when I was giving a tour, we stopped off at the “clock building” and the guy up front turned on the little speaker that gives the nuclear Maser clock time that you hear if you call (202) 762-1401. While I stood at the rear of the group with my cell phone connecting to the time hack number above, you could hear an ever so slight echo from the two systems saying the same thing. You see, the Maser time came out of the server behind the glass while my cell phone provider took the signal and smashed it through the cellular network. The new Admiral was on that particular tour and he really loved the example of network time delays. By the way, as an added bonus, you can set your wristwatch and clocks to the most accurate time on the planet if you call that number listed above. The “Giant Voice” says “US Naval Observatory Master Clock….at the tone it will be…(insert time here).”
A year is one orbit of the Earth about the Sun. A day is one rotation of the Earth about its axis. You keep track of hours and minutes with a set of spring loaded gears or digital circuitry attached to your wrist. And one second is 9,192,631,770 oscillations of an electron between two hyperfine levels in the ground state of a cesium atom. In other words, it comes from an atomic clock like the one at the U.S. Naval Observatory. It therefore seems any practical approach to time involves measuring the duration of some physical process: gears, sand grains, pendulums or electrons. When you do so, you arrive at some surprising results. You see, all this “time” stuff only matters if your gizmos and gadgets are on the same place and not whipping around at the speed of light. In other words, and I’m sorry to say, time is a made-up concept that our species uses to establish a rhythm of life.
Some examples of how our species has made up time over the past five millenia demonstrates our “need” to have “time.” Five thousand years ago, Sumerians in the Tigris-Euphrates valley in today’s Iraq had a calendar that divided the year into 30 day months, divided the day into 12 periods.
Although there are no written records of Stonehenge, built over 4000 years ago in England, its alignments show its purposes apparently included the determination of seasonal or celestial events, such as lunar eclipses, solstices and so on.
The earliest Egyptian calendar was based on the moon’s cycles, but later the Egyptians realized that the “Dog Star” in Canis Major, which we call Sirius, rose next to the sun every 365 days, about when the annual inundation of the Nile began. Based on this knowledge, around 3100 BCE, they became the first civilization on Earth to devise a 365 day calendar. Before 2000 BCE, the Babylonians (in today’s Iraq) used a year of 12 alternating 29 day and 30 day lunar months, giving a 354 day year. In contrast, the Mayans of Central America relied not only on the Sun and Moon, but also the planet Venus, to establish 260 day and 365 day calendars[i].
The calendars of western civilization offer interesting opportunity for study. Originally the Romans numbered years ab urbe condita, that is, “from the founding of the city” (of Rome, where much of the character of the modern world had its beginnings). This calendar did not follow the physical orbit of the planet; had it remained in use, 1996-01-14 would have been New Year’s Day in the year 2749 a.u.c. The “Julian” calendar ran into big problems when the Catholic church ran into problems establishing the day of Easter. Had Pope Paul III done nothing, Easter would have fallen in the Summer by the 16th century. The Pope hired an astronomer, Jesuit Christopher Clavius, to come up with a proper calendar solution. The final calendar was invoked when Pope Gregory was sitting on the throne of the Catholic church and became known as the Gregorian Calendar. This is the calendar we use today.
If you still don’t believe that we “make up” concepts of time, consider the greatest mind of the last 400 years and what he thought about time. Einstein asked us to throw away this picture of time and instead think about our collective motion through both space and time. Einstein said that everything was “relative” to the observer’s position. He called this concept, “Relativity.” In relativity, all objects travel at exactly the speed of light. This velocity can be budgeted between space travel and time travel. If you travel faster through space, you must therefore travel slower through time. Suddenly, folks travelling at different speeds relative to each other would disagree on how much time passes between events.
What’s this about a Light-Year? When we in the space community (the community is just off FM549, by the way) speak in terms of light year, we are just using the concept of time and distance together. We can even represent a light year in mathematical terms. First, one considers the number of seconds in a year (60x60x24x365=seconds in a
year 31536000) then you multiply that value by 186,000 (light travels at 186,000 miles in a second) x 186000 = 5865696000000 miles in a lightyear. So this enormous value is 5865696000000 miles that light travels in a single year! Personally, I would rather say “one” light year, knowing in my mind that it’s a very long way.
When I create an image of something in space, I seldom wonder how far away it is because most of the galaxies I image are in the millions of LY away. When first starting in astronomy back in 2003, I would look at an object and wonder what was happening on our planet when the light left the object. The history books run out of gas pretty quickly on this because there are billions of galaxies that are in the millions or even billions of light years away from Earth. Any image that I make from one of these objects contains ancient photons. I find that an extremely unique and fascinating proposition, to routinely engage with photons that are billions of years old!
All this is not just a fun thought experiment. It can be directly observed. In 1971, two scientists placed four atomic clocks on a jet plane, and flew around the world. They recorded the time that transpired aboard the plane, and found all four clocks disagreed with clocks on the Earth’s surface by roughly 275 nanoseconds (for a Westward trip). Not exactly a tragic loss of accuracy, but a measurable effect!
Speed isn’t the only way to slow down your clocks. When you move deep into the gravitational field of a large object, your time also moves slower. Global positioning satellites orbiting Earth are farther out from the center of Earth’s gravitational pull. As a result, their clocks march at a slightly altered pace. If we did not correct for this difference, the GPS systems would fail miserably in triangulating your position. In fact, triangulating is a poor choice of words here, as it implies three unknowns: longitude, latitude and altitude. In fact, time is also an unknown, and it takes at least four satellites to find where you are.
To see an excellent display of how astronomy really is time travel, see how the Hubble Space Telescope works as a time machine by capturing the faintest photons of light. Check out this video about Hubble Time. If there can be a lunch time and a dinner time, why not a Hubble Time?
I love that idea. Check out this wonderful Hubble video:
Read more by Max Corneau:
- How to buy a telescope
- Earth’s recent encounter with an asteroid is closest in 200 years
- NASA launches Mars Science Lab
Our Universe Today is a column written by Blue Ribbon News special contributor, Max Corneau, who has lived in Rockwall with his family since 2000.
Max retired from the U.S. Army in 2009 as a Lieutenant Colonel, Senior Space Operations Officer and Master Aviator. He amassed over 3,200 hours as a pilot of Special Electronic Mission Airplanes. Since 2004 he has been a NASA/JPL Solar System Ambassador, is a Master of Astronomical Outreach through the Astronomcial League and built his own astronomical observatory. His amazing images can be seen at AstroDad.com.
To submit your news and events or a guest column on your area of expertise, email editor@BlueRibbonNews.com.