this post was submitted on 27 Jul 2023
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UFOs

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[–] DaughterOfMars@lemmy.world -3 points 1 year ago (7 children)

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.

[–] Stoneykins@lemmy.one 1 points 1 year ago (6 children)

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...

[–] DaughterOfMars@lemmy.world -2 points 1 year ago (2 children)

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.

[–] Stoneykins@lemmy.one 1 points 1 year ago (1 children)

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

[–] DaughterOfMars@lemmy.world 1 points 1 year ago

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.

The uranium in the Hiroshima bomb was about 80 percent uranium 235. One metric ton of natural uranium typically contains only 7 kilograms of uranium 235. Of the 64 kilograms of uranium in the bomb, less than one kilogram underwent fission, and the entire energy of the explosion came from just over half a gram of matter that was converted to energy. That is about the weight of a butterfly.

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.

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