this post was submitted on 27 Jul 2023
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I'll put it another way then: any information you intended to send back after you arrive in Sirius would take ~9 years to arrive back home. Due to causality, this means that you cannot interact with Earth in any way for -- at minimum -- 9 years. However, from your perspective, you accelerated at let's say 10 Gs (speed increased by 98 meters per second every second), until you were half-way to Sirius, which will take about 5 months. Then you decelerated at -10 Gs to arrive with 0 speed, another 5 months. You perceive only 10 months of travel, but you are now 9 light-years from home.
The math is not the part which is difficult, and requires only a basic understanding of relativistic physics. The issue is maintaining 10 Gs of constant acceleration for 10 months.
Yeesh I'm just not good at that kind of stuff. Time dialation is what is making this hard for me to wrap my head around, but basically the big issue with this method of travel is you need infinite energy (which might be something these ships somehow do) and its like fast forwarding into the future, so even if you go back immediately it will be like you were gone ~18 years but only experience less than 2.
It is certainly an interesting thing to think about, but sounds depressing in practice. If this is the practical way that some beings have traveled here, I feel like we are missing a piece of the puzzle for long distance space travel. Maybe they have a way to do something about time dilation. Or maybe they just don't ever die...
@Stoneykins @DaughterOfMars Some don't. Some use manufactured bodies.
The energy necessary to accelerate a bit more increases as the speed that object is travelling gets closer to the speed of light and indeed mathematically as the speed of the object gets closer to the actual speed of light the energy necessary to accelerate it gets closer to infinity.
If I remember it correctly it's because in the General Relativity Theory in the acceleration equation (not sure anymore if it was the one that relates Force to Acceleration or the Acceleration and Velocity one) the mass of the object isn't actually a constant amount but depends on its current velocity (it's as if the mass became larger with velocity). Just like for the whole time dilation stuff, this effect comes from the main equations and only really becomes noticeable closer to lightspeed (i.e. at relativistic speeds, called that because that's when you notice the effects of the Theory of Relativity, such as time dilation).
So the energy necessary to get to speeds below lightspeed yet close enough to have relatistic effects is not at all infinite, hence it is possible to reach relativistic speeds with the whole time dilation, redshift of light and other such effects, maybe even with current technology (I think we already have the tech to accelerate a ship to near lightspeed by having ground-based lasers pointed at a mirror on the back of it (so the light gets reflected - though that stuff has incredibly low acceleration as you're literally pushing that ship with photons plus ground-based lasers inside the Earth's athmosphere would was tons of energy due to the athmosphere).
In fact the very same experiments with subatomic particles that showed time dilation effects in their decay (which I mentioned in another comment) also showed it is possible to accelerate something to the point of having time dilation effects without infinite energy (if it happenned then it was possible to make it happen :))
Those effects only occur from the perspective of, for example, Earth. If you could exert force upon a space ship traveling away from you, it would require more energy to continue to accelerate it as its speed increases relative to you. But from the reference frame of the ship, this does not hold. Now, of course it will still require an insane amount of energy to maintain a constant acceleration, but from the spaceship's perspective energy expenditure is constant (assuming the mass of the ship isn't changing due to fuel loss).
If I remember it correctly from the point of view of the ship it looks like the propulsion becomes less effective, tough I confess my recolection of what I learned about the General Theory Of Relativity in my Physics degree almost 3 decades ago (which I never completed, by the way, so I'm an EE not a Physicist) breaks at around this point so I might be completelly off on this.
You don't need infinite energy, to be clear. Mathematically, you would need infinite energy to cross the light-speed barrier, which is why we don't believe that it is possible. You would simply need a LOT of energy. How much would depend on the mass of the craft. Actually the bigger problem may be negating the internal G forces, as humans cannot survive 10 Gs for long (or at all), but again it seems that these UAPs are capable of that.
Ah, I misread a wiki page. Not infinite, since we aren't traveling lightspeed, but approaching infinite as we approach lightspeed? Which is to say, not infinite but dang thats a lot of energy?
Again, I'm not great at understanding this stuff, so thanks for being patient
Sure, I don't mind explaining. No, we would not need near-infinite energy. We are quite capable of accelerating at 10 Gs in space right now, but eventually you will run out of fuel. So, let's say you add more fuel, well now you have more mass to accelerate so it costs more fuel per second. This becomes a balancing act which we can not overcome for long, and it's the reason space shuttles are so complicated and have multiple stages which break away to reduce mass.
This is primarily an issue because we use quite simple propulsion techniques, which rely on Newton's third law -- that forcing mass out from behind a ship will propel it in the opposite direction. It may be possible to accelerate using an Electro-Magnetic field, which would not involve burning fuel but instead some kind of depleting battery storage, or perhaps a nuclear reactor. In this case, accelerating at 10 Gs is simply a matter of matching the energy requirements to the mass of the ship, and for some perspective on the energy capabilities of nuclear fission, the Little Boy bomb reacted less than a gram of nuclear material to create the explosion in Hiroshima.
So, obviously we aren't capable of converting that energy into a useful method of propulsion yet, but have some heart, because the pieces are all there -- we just need to put them together.