Post by auntym on Oct 24, 2023 13:16:27 GMT -6
lithub.com/ufo-or-uf-no-what-would-take-for-aliens-to-visit-our-solar-system/
UFO or UF-No: What Would Take for Aliens to Visit Our Solar System?
Adam Frank on Interstellar Travel, Technology from Sci-Fi, and the Physics of Both
By Adam Frank / lithub.com/author/adamfrank/
October 24, 2023
I’m going to give you the bad news first. The distances between stars are so large that they might be impossible to routinely cross. Sure, maybe you send robot probes that reach their target in two hundred years (and then you need another century or so for a message to get back). But the possibility that you, I, or anybody else can pop around to the best vacation planets in the galactic empire may simply be excluded by the laws of physics.
Or maybe not.
This is the kind of landscape we have to deal with when we try to navigate the question of aliens and interstellar travel. We absolutely, positively know the distances between the stars. We also know for certain that the universe imposes a speed limit when it comes to crossing those distances. What we need to do next is imagine, based on what we know about the structure of reality, how aliens might get around those limits.
If UFOs are spaceships from other star systems, then how might they (or us in the future) cross the great interstellar voids? The first thing we need to address this question is an understanding of just how big, big, biggity-big space really is (to paraphrase the great Douglas Adams). Yeah, I know you think you know how big space is, but trust me, it’s bigger. Every time I have to deal with these kinds of distances in my research, my capacity for freaking out at the scale of the cosmos (even our wee corner of it) is entirely and forcefully renewed.
Astronomers measure interstellar distances in light-years, which, I know, is confusing. A light-year is the distance light travels in a year and spans six trillion miles. That’s a six with twelve zeros after it—6,000,000,000,000 miles. You have probably walked a mile and driven thousands of miles. All this takes you through only the first three zeros. The other nine require a heroic feat of imagination. If you’re looking for a familiar comparison, it’s the same as traveling all the way around the Earth hundreds of millions of times. Imagine how many connecting flights and pointless waits getting stranded in O’Hare Airport that would imply.
Another way to understand a light-year is to consider the distance from the Sun to the edge of the solar system. If the Milky Way galaxy is our local city of stars, then the solar system is the house we were born in, and Earth is one room in that house. In 2006 we launched the fastest space probe ever developed, New Horizons, and sent it to Pluto, which can stand in for the edge of the solar system. The distance to Pluto is about one thousand times shorter than a light-year. Our solar system, where all human activity on planets and in space has played out, is a tiny fraction of a light-year across.
Even if we stay in our local neighborhood, the distance to the nearest interstellar Starbucks has to be measured in hundreds or thousands of light-years.
And here’s the real point to ponder: even though New Horizons was hurtling through space at 36,000 miles per hour, it still took about ten years to reach Pluto. From that factoid, we can conclude that it would take New Horizons at least twenty thousand years to travel a single light year. That’s a very long time, but it still doesn’t even get us all the way to interstellar distances. There’s nothing much out there at one light-year away. The Oort Cloud, where most of the solar system’s comets live in cold storage, extends out to around a light-year, so even out at this distance, you’re still technically in the solar system.
You have to travel around three more light-years to reach the nearest star, Alpha Centauri. A journey by New Horizons to that star would take around eighty thousand years, and most stars are way, way farther away than Alpha Centauri. The Milky Way galaxy is about a hundred thousand light-years across. Even if we stay in our local neighborhood, the distance to the nearest interstellar Starbucks has to be measured in hundreds or thousands of light-years. That would be tens of millions of years of travel time for our fastest space probes.
All of this serves to confirm that, yes, space is frackin’ big. If UFOs really are interstellar visitors, then these are distances they must routinely cross. These are also the distances we must learn to cross if we are to become an interstellar species, aliens to someone else.
Any attempt to traverse those distances runs into a fundamental fact about the universe. Nothing can travel faster than light speed. This is not just a fact about light. It’s a fact about the very nature of physical reality. It’s hardwired into physics. The universe has a maximum speed limit, and light just happens to be the thing that travels at it. Actually, any particle without mass (like light) travels at light speed, but nothing anywhere can travel faster.
This speed limit is so fundamental that it’s baked into the existence of cause and effect. The finite speed of light is what forces effects to come after causes like dishes shattering only after they get knocked off tables.
There may, of course, be more physics that we don’t know about that’s relevant to this question of interstellar travel. Still, this speed-of-light thing is so important to all known physics that if you want UFOs to be spaceships, you can’t get around it by just saying, “Oh, they’ll figure it out.” You gotta work harder than that.
Now let’s dig into the problem. Given these insane interstellar distances, how can we extrapolate from the physics we do understand to see how those aliens (or us in the future) might cross the cosmic void. We have a few possibilities:
Generation Ships: Depending on their biology, the life span of our hypothetical aliens might be shorter than the centuries-long journey required for slow sub-light-speed travel between stars. This is certainly the case for us. If you are awake the whole trip, you’ll be dead by the time you get there. One way around this dead-on-arrival dilemma is to have children along the way. You’ll still be dead, but your kids or grandkids or great-great-grandkids’ offspring will make it.
Generation ships (also called century ships) are one way that interstellar travel might be possible. Those ships would have to be pretty big, though, to carry an entire colony of space travelers. It would be hard to miss one of these if it pulled into orbit. Also, you might imagine that those grandkids would be pretty *angry* off about having to spend their entire lives on a smelly space cruiser. Maybe the kids are the ones erratically flying the UFOs; that could explain a lot.
CONTINUE READING: lithub.com/ufo-or-uf-no-what-would-take-for-aliens-to-visit-our-solar-system/
UFO or UF-No: What Would Take for Aliens to Visit Our Solar System?
Adam Frank on Interstellar Travel, Technology from Sci-Fi, and the Physics of Both
By Adam Frank / lithub.com/author/adamfrank/
October 24, 2023
I’m going to give you the bad news first. The distances between stars are so large that they might be impossible to routinely cross. Sure, maybe you send robot probes that reach their target in two hundred years (and then you need another century or so for a message to get back). But the possibility that you, I, or anybody else can pop around to the best vacation planets in the galactic empire may simply be excluded by the laws of physics.
Or maybe not.
This is the kind of landscape we have to deal with when we try to navigate the question of aliens and interstellar travel. We absolutely, positively know the distances between the stars. We also know for certain that the universe imposes a speed limit when it comes to crossing those distances. What we need to do next is imagine, based on what we know about the structure of reality, how aliens might get around those limits.
If UFOs are spaceships from other star systems, then how might they (or us in the future) cross the great interstellar voids? The first thing we need to address this question is an understanding of just how big, big, biggity-big space really is (to paraphrase the great Douglas Adams). Yeah, I know you think you know how big space is, but trust me, it’s bigger. Every time I have to deal with these kinds of distances in my research, my capacity for freaking out at the scale of the cosmos (even our wee corner of it) is entirely and forcefully renewed.
Astronomers measure interstellar distances in light-years, which, I know, is confusing. A light-year is the distance light travels in a year and spans six trillion miles. That’s a six with twelve zeros after it—6,000,000,000,000 miles. You have probably walked a mile and driven thousands of miles. All this takes you through only the first three zeros. The other nine require a heroic feat of imagination. If you’re looking for a familiar comparison, it’s the same as traveling all the way around the Earth hundreds of millions of times. Imagine how many connecting flights and pointless waits getting stranded in O’Hare Airport that would imply.
Another way to understand a light-year is to consider the distance from the Sun to the edge of the solar system. If the Milky Way galaxy is our local city of stars, then the solar system is the house we were born in, and Earth is one room in that house. In 2006 we launched the fastest space probe ever developed, New Horizons, and sent it to Pluto, which can stand in for the edge of the solar system. The distance to Pluto is about one thousand times shorter than a light-year. Our solar system, where all human activity on planets and in space has played out, is a tiny fraction of a light-year across.
Even if we stay in our local neighborhood, the distance to the nearest interstellar Starbucks has to be measured in hundreds or thousands of light-years.
And here’s the real point to ponder: even though New Horizons was hurtling through space at 36,000 miles per hour, it still took about ten years to reach Pluto. From that factoid, we can conclude that it would take New Horizons at least twenty thousand years to travel a single light year. That’s a very long time, but it still doesn’t even get us all the way to interstellar distances. There’s nothing much out there at one light-year away. The Oort Cloud, where most of the solar system’s comets live in cold storage, extends out to around a light-year, so even out at this distance, you’re still technically in the solar system.
You have to travel around three more light-years to reach the nearest star, Alpha Centauri. A journey by New Horizons to that star would take around eighty thousand years, and most stars are way, way farther away than Alpha Centauri. The Milky Way galaxy is about a hundred thousand light-years across. Even if we stay in our local neighborhood, the distance to the nearest interstellar Starbucks has to be measured in hundreds or thousands of light-years. That would be tens of millions of years of travel time for our fastest space probes.
All of this serves to confirm that, yes, space is frackin’ big. If UFOs really are interstellar visitors, then these are distances they must routinely cross. These are also the distances we must learn to cross if we are to become an interstellar species, aliens to someone else.
Any attempt to traverse those distances runs into a fundamental fact about the universe. Nothing can travel faster than light speed. This is not just a fact about light. It’s a fact about the very nature of physical reality. It’s hardwired into physics. The universe has a maximum speed limit, and light just happens to be the thing that travels at it. Actually, any particle without mass (like light) travels at light speed, but nothing anywhere can travel faster.
This speed limit is so fundamental that it’s baked into the existence of cause and effect. The finite speed of light is what forces effects to come after causes like dishes shattering only after they get knocked off tables.
There may, of course, be more physics that we don’t know about that’s relevant to this question of interstellar travel. Still, this speed-of-light thing is so important to all known physics that if you want UFOs to be spaceships, you can’t get around it by just saying, “Oh, they’ll figure it out.” You gotta work harder than that.
Now let’s dig into the problem. Given these insane interstellar distances, how can we extrapolate from the physics we do understand to see how those aliens (or us in the future) might cross the cosmic void. We have a few possibilities:
Generation Ships: Depending on their biology, the life span of our hypothetical aliens might be shorter than the centuries-long journey required for slow sub-light-speed travel between stars. This is certainly the case for us. If you are awake the whole trip, you’ll be dead by the time you get there. One way around this dead-on-arrival dilemma is to have children along the way. You’ll still be dead, but your kids or grandkids or great-great-grandkids’ offspring will make it.
Generation ships (also called century ships) are one way that interstellar travel might be possible. Those ships would have to be pretty big, though, to carry an entire colony of space travelers. It would be hard to miss one of these if it pulled into orbit. Also, you might imagine that those grandkids would be pretty *angry* off about having to spend their entire lives on a smelly space cruiser. Maybe the kids are the ones erratically flying the UFOs; that could explain a lot.
CONTINUE READING: lithub.com/ufo-or-uf-no-what-would-take-for-aliens-to-visit-our-solar-system/