The Universe at walking speed

There’s a certain familiarity we all have with how long it takes to get somewhere on foot.  Taking something well known to us like walking, I thought I’d attempt to use this as a measuring stick for the stars. The preferred walking speed for most people is around five kilometers for one hour spent walking (5 km/hr).  I know some fast walkers get up to 9 km/hr or more, but I’m going to use a comfortable gait that we’d want to stick to for long periods of time since walking takes time especially when you have a long way to go.
This week NASA announced that it has found 7 new planets around a small star that is 39 light years away from us. This star and its planets are named the Trappist-1 system.

A friend asked me this week, So, how many years in a light year again?Of course, there is one year in a light year, but what he was inferring was, “How bloody far away is that if we wanted to get there?”

The speed of light is 299,792,458 m / s

At the speed of light, light can travel the distance of 9,454,254,955,488,000 km in 1 year  (9.45 trillion km)  (or 9.454 x 1012 km)
The fastest man made object ever created [on record by NASA] was the Juno spacecraft that was sent to Jupiter.  It got up to the incredible speed of 265,000 km/h.  That’s like Mach 214, but in outer space no one can hear you scream as you go by that fast.

For our fastest spacecraft Juno, it would take ~35,701,132 hours or 1,487,547 days or about 4075 years to travel 1 light year and to span the distance of 39 light years, it would be 39 x 4075 years = 158,925 years for our fastest spacecraft to reach these newly discovered planets!

That’s a long wait to get there.

If we were to drive to Trappist-1 in a car at an average speed of 100 km/hr it would take 10.8 million years per light year x 39 light years  =
that’s 421.2 million years now that’s a long drive.
If you had to walk to the Trappist-1 system (at a constant rate of 5 km/hr without stopping once), it would take over 8.4 billion years for you to get there!

The estimated age of the earth is 4.5 billion years. The estimated age of the universe is 13.8 billion years.

Fortunately red dwarfs like the star in the Trappist-1 system live a long time (estimates are 10 trillion years, although I’m not sure how reliable those estimates really are), but chances are that the star will still be there by the time you get there in 8.4 billions years from now.  Well, that’s assuming it’s moving in the same relative direction as our sun.

Our solar system, and probably most of our neighbouring star systems, are spinning around our galaxy.  It is estimated to take 225-250 million years to do a full turn.  So over a period of 8.4 billion years, our solar system would have gone around our entire galaxy somewhere between 33 to 37 times.
The Juno spacecraft is always traveling at a the same speed after its initial acceleration by rocket or when it gets a speed boost from a ‘gravity slingshot’ around a planet or moon.  However, if the spacecraft we send were to accelerate throughout the first half of the trip, always gaining speed and then it were to flip around and decelerate for the second half to slow down enough by the time it gets there, we could probably get there much much quicker.  This sort of thing might be possible with the ‘impossible EM drive‘, if it works.  A continuously powered engine similar to that might be used to get to our closest stellar neighbours in a couple of centuries rather than 160 millennia.  I’m not sure how fast this ship would get, perhaps at the halfway mark it could be as much as 20% the speed of light?  I’m speculating, I think it depends on how quickly it’s accelerating, but if it’s continuous acceleration then it doesn’t have to be that much.  Of course, some people argue that faster than light travel is possible (even though Einstein thought otherwise).

For us to send a message to the Trappist-1 system, it would take 39 years and then we’d have to wait another 39 years for the answer to come back to us assuming they receive the message and respond back right away.

In comparison, when light leaves the sun and travels roughly 150 million km to hit earth, it only takes 8 minutes to cover that distance.  So for us to talk back and forth with an astronaut near the sun, it’d take 8 minutes each way.

Venus is only 6 minutes away from the sun at light speed and Mercury is only 3.2 minutes!  Mars 12.6 minutes, Jupiter 43.2 minutes, Uranus 159.6 minutes, Neptune 4.1 hours, Pluto 5.5 hours!

Imagine if we turned on a laser beam to signal to the Trappist-1 system.  After turning on the beam of light, it would shine past Pluto within five and a half hours on the first day of the trip but we then would have to wait 39 years before it is seen by someone on one of those planets.  That is, assuming they were looking for it and that there were such an incredibly bright laser beam like that.

If there ever were such a thing as a laser beam that curved in such a way that it followed the curve of the earth’s surface, we could shine a beam around the world.  You know how long it would take for that light to go around the planet and hit you in the back of the head after turning it on?  Roughly 1/10th of a second which is actually quicker than the average blink of an eye (which is typically 300 to 400 milliseconds).

In comparison to walking to a nearby star, how long would it take to walk around the world?  Well, Jean Béliveau left Montreal and visited 64 countries and hiked over 75,500 km in 11 years.  That’s like walking around the earth twice (the earth’s circumference is 40,075 km).

Walking to California from Ottawa (~4,687 km) would take you just over a month of continuous walking without a single break (about 39 days). If you ran all the way without stopping once, you could do it in about 13 days.  Most likely you could only run at that speed for about 8 hours a day. If you’re a super human runner, it would take about 39 days at the same speed (15 km/hr) for a full 8 hours every day. That would be like running 3 marathons every day.  There would be 111 marathons (42 km each) between California and Ottawa. I can’t imagine anyone doing such a thing ever.

Surprisingly, Katie Visco ran just over 5,040 km from Boston to San Diego in 276 days.  That’s the equivalent of 120 marathons in 276 days.  Wow!
You would have to run 8.7 trillion marathons to reach Trappist-1 and to think that Trappist-1 is pretty close to us!  A mere 39 light years (that’s only about 12 parsecs).

The center of our galaxy is estimated to be ~26,666 light years from here (about 8 kpc). A parsec is 3.26 light years, a kiloparsec (kpc) is 1,000 parsecs.
The center of our galaxy is 252,281,692,800,000,000 km (or 252 quadrillion km) from us. That’s just to get to the middle from where we are on one of the arms.  The whole galaxy is about 100K light years across, but our galaxy isn’t even that big compared to the biggest known galaxy.

The “IC 1101” galaxy is about 6 million light years wide (about 60 times bigger and 20,000 times more massive than our milky way galaxy).
There are 100 to 200 billion galaxies in the observable universe. The observable universe is estimated to be about 93 billion light years across (about 28.5 gigaparsecs).

The actual size of the universe is assumed to be bigger and might be infinite depending on who you talk to but that’s for another post.  How long would it take to walk across the part of the universe that we can currently see with our radio telescopes?  I won’t go into the fact that what we see expands over time or that the universe itself is believed by many astronomers to be expanding at an accelerating rate which would make it difficult to ever reach your end point especially if you’re walking.  Of course, you can’t actually walk in space without anything to walk on so we could substitute walking with ‘slow floating at a constant rate of 5 km/hr‘ assuming you never get pulled into a nearby star or such.

Distance of 1 light year times the number of light years to span the observable universe:
9,454,254,955,488,000 km x 93,000,000,000 light years =
8.7924 x 1026 =
~879,240,000,000,000,000,000,000,000 km

divide by a constant slow floating speed of 5 km/hr =
1.75848 x 1026 hrs
/ 24 hrs / 365 days =
20,073,972,602,739,730,000,000 years
It would take 20 sextillion years to walk across the observable universe!

As they say, if you walk a mile in my shoes you’ll end up at the bar. 😉

3 Replies to “The Universe at walking speed”

  1. 1 kilometer = ~1320 steps
    Distance to your corner store
    1 million steps = 757.5757.. Km
    ~distance from Toledo OH to Nashville
    1 billion steps = 757,575.7575.. Km
    ~distance to the moon and back (just short)
    1 trillion steps = 757,575,757.5757.. Km
    Average distance give or take to Jupiter from the sun

  2. At first I rounded these numbers not realizing just how big a difference that makes well 3 extra zeros for the final number. The time it would take to slowy drift across the observable universe might be 20 sextillion years.
    But how do we know that the observable universe is 93 billion light years across as claimed?
    To my understanding, this depends on knowing the age of the universe and on measuring the redshifts of Cepheid variables (pulsating stars in distant galaxies) which assumes that these stars have certain properties, such as how big they can get, how long they might last, how they might form and their composition. However, this also assumes that redshifts measured from these distant pulsating stars are the result of the expansion of the universe. In other words, redshifts are the result of light being shifted toward the red end of the spectrum due to the speed in which the stars are going away from us (very quickly to say the least). It also relies on the premise that the measured redshift is not caused by anything else.
    However, measuring the redshift of stars isn’t the only way to measure star distances. At least not for stars that are much closer to us.
    The Gaia satellite will measure the position and motion of over 1 billion stars to create a three-dimensional map of the Milky Way.
    Gaia’s mission: solving the celestial puzzle.
    I know this is unrelated to redshift measurements, but I’m hoping that the data from the Gaia satellite will help us confirm the size of our galaxy. I know, now you’re wondering how do they measure the size of our galaxy? Well…

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