Air pressure works like water pressure. The deeper you go in water, the more the pressure because of the weight of the water above. Similarly, the lower you go in the atmosphere the more the pressure. At sea level, air pressure is normally about 14.7 pounds per square inch. This can be measured with an altimeter, which is used on aircraft.
Mount Everest is so high that climbers usually need to carry oxygen to go the summit. Commercial airlines go even higher.
When you get about 62 miles up (100 km) you’re at air pressure that is basically zero and you are above most of the atmosphere altogether.
The International Space Station orbits around 250 miles up, but there is still some, very thin atmosphere up there that eventually slows down the ISS, requiring it to be boosted once in awhile.
Eventually you come to deep space, and there are some molecules floating around out there, just not very many. So space isn’t completely empty, just mostly empty. Sometimes there are molecular clouds in space in regions where stars are forming, and the molecules floating around are a little denser.
If you went outside on a spacewalk on your way to Mars, took an empty bottle with you and opened it and then sealed it, once inside the spaceship you’d find your bottle had nothing but a vacuum in it. The free floating molecules out there are so sparse you’d not find any inside your little bottle.
The human race will be much changed. The reason the golden record was included on the Voyager spacecrafts was twofold. The main reason was a mechanism to inspire public interest (and therefore funding) for the project, which was to explore the outer planets in our solar system and interstellar space. The other reason was that Voyager I was going to pass within 1.6 light years of the star called Gliese 445 in about 40,000 years. In case any intelligent space traveling beings over there might notice Voyager I drift by their star 1.6 light years away, they might go out, retrieve it, and discover the Golden Record.
To compare that to us, if an alien spacecraft the size of Voyager I passed by within 1.6 years of our own sun we would not be able to detect it. It’s too small, and out many times farther than the Voyagers are now from Earth. It would be many times outside the solar system entirely.
Now, let’s assume that 40,000 years from now Voyager I is drifting by within 1.6 light years of Gliese 445 which is 17.1 light years away from us and alien astronomers on a planet over there did somehow notice it. Let’s say their alien scientists then launched a probe to investigate and find the Golden Record. What would happen? That’s the essence of your question, right? Well, let’s look at it.
To send a probe from an alien world to Voyager I as it passes by the star Gliese 445 their probe would have to travel 1.6 light years, which would take thousands of years. But once reaching Voyager I, the probe could communicate back to their alien world in only 1.6 years, with a 3.2 year return signal. So let’s say they did it.
The Golden Record is designed to indicate to an advanced alien civilization that other intelligent beings are “out there.” This would be extremely exciting for them to realize someone else (Earth) is out there. They might try to send a radio signal in our direction to let us know the message was received. The message would take 17.1 years to reach Earth, so basically, 45,000 years from now the message from the aliens might reach Earth, but would anyone still be around to listen? My estimate of time is the 40,000 years for Voyager I to reach that far, another 4,000 years or so for their space probe to reach Voyager, and a few years communicating with the probe to figure out what it found. Nothing here is true math. It’s just very round, hypothetical numbers.
Once the aliens realized there was another planet with intelligent beings on it, they might try to communicate with us even though we are more than 17 light years from them.
So a form of communication could eventually be established. Considering the speed of light with a return message taking 34 or 35 years (the time in light years and back) it would be a slow, gradual communication. Interstellar travel between the two civilizations would not be feasible, however. It would take the spacecraft about the same time as it took Voyager, or maybe they could half the time with some kind of alien propulsion system. UFO conspiracies aside, travel over those distances isn’t realistic.
The best could be communication.
Then again, the human race will probably be much changed 45,000 years from now and who knows if anyone will be listening by then, or conversely, if there is an alien civilization orbiting on a planet around Gliese 445 now, will they still be around by the time Voyager I reaches there?
Some people on Earth would not believe it or even care. Scientists, if there are any scientists left 45,000 years from now would be excited. I’d imagine it would be about the same for the aliens, but who knows what kind of organization they might have over there.
Basically, it would be largely ignored by the public.
Actually, this is an interesting question and I think I can provide an interesting answer.
To know what the people of the world want aliens to know about us, look no further than the Voyager spacecrafts. When we launched them in 1977 they were on a mission to explore the planets in our solar system, but afterward it was known they would be flung out of our solar system to drift in interstellar space for tens of thousands of years, and interstellar space is where they are both now.
So physicist Carl Sagan had an idea to place a golden record on each spacecraft with a message from Earth to any aliens who might come across them in the eons to come. According to Wikipedia, “The records contain sounds and images selected to portray the diversity of life and culture on Earth, and are intended for any intelligent extraterrestrial life form who may find them. The records are a sort of time capsule.”
So what’s exactly on this record, and what did mankind in 1977 want future aliens in space to know about us? The contents of the record were decided by a committee from Cornell University and headed by Carl Sagan. It took more than a year to decide on the contents, and contains 115 images of Earth and natural sounds of the planet like wind, surf, thunder and whales.
There’s images of DNA and music by Mozart and Beethoven and a whole bunch of other stuff to indicate we are an intellectually and culturally developed civilization of beings.
Yes, I believe in space aliens, and unlike others, no, I don’t believe they are “here” nor do I ever think they will ever be able to come here, nor us go there.
Space is so big, that given we’ve been emitting radio waves for over a hundred years, the radio “sphere” in space coming from us hardly encompasses very many stars at all. We live in a huge galaxy, one of billions of galaxies, and in our little corner of our galaxy our radio waves, traveling at the speed of light, haven’t even reached a significant portion of our own galaxy.
In the image below, you can see just how tiny an area that is, represented by the small blue circle, or dot.
That being the case, unless there are aliens that want to visit us and “hide among us” (for whatever reason), they’d really have to come from somewhere pretty close.
I don’t see it.
Regarding “UFOs,” aka unidentified objects in the sky, there are many natural phenomena that we don’t yet understand, but to take it there is something we have yet to identify and then extrapolate that it is some kind of alien spacecraft visiting across thousands of light years just to come here, is more than a stretch. It’s not science.
This is the kind of question, “How do we get to Mars?” that normally would take a lot of discussion and involve a whole lot of mathematics.
I’m going to try to explain it simply and to the best of my limited ability.
Mars is in orbit around the sun. Earth is in orbit around the sun. Earth, being closer to the sun, orbits faster. Mars orbits more slowly. So you have to wait until the two planets are lined up to launch, which happens about every 2 years or so. But it’s not a straight shot out to Mars. Everything works following the rules of orbital mechanics.
Essentially, we launch a spacecraft from Earth into a highly elliptical orbit around Earth. This orbit is so elliptical, that it extends all the way out to the orbit of Mars. You time it so just as this spacecraft reaches it’s farthest point from Earth before beginning it’s return journey, Mars comes along in it’s orbit. The spacecraft meets up with Mars.
The image above from the Jet Propulsion Laboratory website of NASA illustrates how this transfer of an elliptical orbit from Earth catches up to Mars. This process takes about 9 months for a spacecraft like this to reach Mars, and can be accomplished only about once every 2 years.
byWayne Boyd Studied Physics (college major) & Psychology (college major) at St. Mary’s University, San Antonio, TX
You see, each planet orbits the sun at different speeds. Those planets orbiting closest to the sun, like Mercury and Venus, orbit faster. Further out from Earth, Mars takes about 2 years to orbit the sun. Further out, Jupiter, Saturn, Uranus and Neptune all take progressively longer. Then the sun itself is orbiting the galactic center once every 250 million years, and the Milky Way galaxy is moving toward the Andromeda Galaxy at about 67 miles per second. So no planet will ever be in the exact position it was before, ever. The first image shows the planets orbiting the sun in relationship to our own solar system. The second image shows the planets orbiting our sun in relationship to the sun orbiting the galactic center of the Milky Way Galaxy.
We are in a galaxy with a lot of stars. It is estimated to contain 100–400 billion stars, The nearest galaxy to ours is Andromeda, but the stars within our galaxy, the Milky Way, are from about 4 light years away to about 100,000 light years away. We can see the Milky Way with the naked eye, and it looks, to the naked eye, like a light smear of milk across the night sky. You can’t see the individual stars that are far away, even within our own galaxy. In the Milky Way galaxy there are, as I said, many stars, but in our night sky we can only see about 9,096 individual stars.
I’m a hypothetical billionaire, so let’s discuss financing this project and the chances of success, what we’ll need to get it done, and so forth. Theoretically, it would seem possible.
At the south pole the earth is 12,715 and a half miles in diameter, or about 7900 miles to the center, but at the equator the diameter is 12,756.32 kilometers or 7,926.41 miles to the center. The earth is thicker at the equator and it would take a deeper hole to drill from there. We can make a drill 12.7 miles shorter if we drill from Antarctica. So let’s start drilling there.
From Antarctica, our drill will need to be 3,950.5 miles long to reach the center of the Earth. That’s 300 miles longer than the distance between New York and Paris.
To build a drill like that we’ll have to use a modular design. We’ll start with a shorter drill bit and keep making it longer as we drill deeper until it reaches 3,950.5 miles long.
The drill would need to be really thick and made of some really strong stuff to get through granite and just generally tough layers of rock. A drill tip with diamond heads is probably the way to go. As we drill down, the bit will get dull from time to time and we’ll have to pull the whole drill bit out to replace the head. That might have to be done several times a day.
Can you imagine being 2,000 miles deep at some point and have to pull the whole bit out to replace the head? Sounds like a logistic problem that might slow us down.
Eventually, at some depth or other, we’re going to encounter molten rock. In the core itself is molten iron. Our drill bit will melt. All that trouble for nothing.
It doesn’t sound practical to drill to the center-most point of the earth by drilling from anywhere.
In theory, space is nothing, so the bottle will have a vacuum – an empty bottle. In reality, space is not empty, just mostly empty, so the bottle might have a molecule or two, but most likely it will have nothing.