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Seven earth-sized planets discovered circling a star 39 light years from Earth

nature.com

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Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#311

Post by intrasight »

wallace_f wrote: post #260
chris_va wrote: post #204

Earlier quoted context omitted.

You are technically travelling at 99.99999% of the speed of light right now, relative to something.

What determines my speed limit? Is it set at 0 here on earth? What if I travel to another galaxy, this one was going at .5c relative to me when I was on earth. Then after trillions of years, inflation causes all of the galaxies to separate beyond sight from me in this new galaxy. Now, the centre of this galaxy appears at rest. Does my velocity get "reset?"

inflation/expansion of space is not limited to the speed of light.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#312

Post by blueprint »

drzaiusapelord wrote: post #296
blueprint wrote: post #217

Earlier quoted context omitted.

I'm talking about establishing a self-sufficient colony somewhere other than Earth. We have a major crisis on our hands. And few are even willing to consider let alone research and confirm that we're talking about an extinction event much sooner than we thought, maybe on the order of just a couple years out. Problem is, we don't know. Bigger problem is, we're not doing anything about it.

If its affordable to send people to an off world colony then its affordable to bomb it when war on Earth breaks out. Fleeing isn't going to help in a wartime situation and the idea it will not be targeted by world powers is a little naive.

I said nothing about war..?

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#313

Post by mjmahone17 »

DanBC wrote: post #44
e0m wrote: post #33

To get a spacecraft there it would take: Accelerating at 1g the 1st half, and decelerating at 1g the 2nd half, the traveler would experience 7.3 years of time. For observers it would take 41.8 years at a max speed of 0.998c If you had a near perfect hydrogen -> helium fusion engine, it'd take about 6 million tons of fuel (about the mass of the Pyramids of Egypt or 2,000 Saturn V rockets)

How much fuel would it take to get 6 million tons of fuel off Earth into the interstellar ship?

Are we willing to use a railgun, with a rocket burn at apogee? (So one-half orbit from the starting point: without the burn, the object will hit the ground when it completes its orbit). If so, a lot less than is needed by pure rocket burns, where you have to carry all of the mass used to accelerate to orbital velocity.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#315

Post by semaphoreP »

infogulch wrote: post #247
semaphoreP wrote: post #200

Earlier quoted context omitted.

It's almost all Hydrogen/Helium gas. Other larger atoms and molecules are known to exist in the interstellar medium, but it's primary gas. Also, a good way to remember the density is ~1 Hydrogen atom per cm^3.

How about intergalactic densities?

Don't know the number off the top of my head, but it should be considerably less. It should also be highly varying as some galaxies live in pretty densely packed environments (galaxy clusters), which some live in very open environments like our own galaxy.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#316

Post by semaphoreP »

sand500 wrote: post #264
semaphoreP wrote: post #125

Earlier quoted context omitted.

It'll be in the near-infrared, but the light won't be separated from the star. How they observe the atmosphere is that when the exoplanets transit, they block out different amounts of light at different wavelengths. From that, one can deduce an atmospheric spectrum.

Would using a shield to block out the star be good enough to image the planets? https://en.m.wikipedia.org/wiki/New_Worlds_Mission

It will depend on the size of the telescope, but for all practical purposes, these planets are too close to their star to see directly. A starshade will be good for Earth-like planets at Earth-like separations around Sun-like stars though.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#317

Post by dragonwriter »

mi100hael wrote: post #284
criddell wrote: post #168

Earlier quoted context omitted.

That's essentially what blueprint said. You didn't have any trouble figuring out what blueprint was saying, right?

It's an incorrect and jarring usage of the phrase. Plenty of folks on HN are non-native speakers who benefit from knowing when colloquialisms are used incorrectly.

The transitive form "Begs the question " is long attested, quite common, very clear and readily distinguishable from the intransitive form "Begs the question" [with no direct object], which refers to the petitio principii fallacy, when people prefer a translation into somewhat archaic English to the Latin.

In fact, the attempts I've seen to quantify usages (including those by prescriptivist pedants still trying to pedal the idea that the intransitive usage is the only correct one) find the transitive usage to be the most common, even in publication.

The intransitive use can even be seen as a generalization and rationalization of the transitive use, wherein the transitive use becomes equivalent to the intransitive use with an implied direct object of "the question which the argument was intended to resolve", which (while not the original etymology of the intransitive form) actually makes the intransitive form sensible and has a closer relation to the modern English sense of the words in the phrase than the original etymology of the intransitive usage.

Prescriptivist pedantry on this point is, if this is possible, even more obnoxiously pointless than that directed against the singular usage of "they".

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#318

Post by tajen »

longerthoughts wrote: post #136
Sharlin wrote: post #50

Earlier quoted context omitted.

They are still in separate orbits so the straight line between any two varies greatly in length... not to mention intersecting the star regularly.

Regular shuttles for interplanetary travel timed with periodically favorable orbital positions?

At that distance, gravity must be really fun. Tides are not only for water, such tides can also change the height of mountains, the balance of high-rise buildings, infer on volleyball rules, make you fart because of changes in atmospheric pressure, or... be leveraged to generate electricity. Those guys have simili-infinite energy at human scale.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#319

Post by OscarCunningham »

wallace_f wrote: post #63
ionwake wrote: post #5

Earlier quoted context omitted.

It's a Trap ;) On a serious note, if we can travel close to the speed of light , say 95%, using for example, nuclear rockets, how long would it take to arrive ? ( from the travellers perspective )

The answer for an outside observer is: @ 1g of acceleration it would take 11 months to accelerate to the speed of light. A formula you can put in Google is: (285000000/9.8)/(60x60x24). So 39-(.475x2) = 38, and 38/.95 = 40. So 42 years is your answer . I have no idea how to calculate the relativistic spaceship's elapsed time. It's all wishful thinking. The fastest thing man has created, the Juno spacecraft, travels, b…

This isn't how it works. As you approach the speed of light acceleration becomes less effective (i.e. you feel 1g but don't get faster at 10m/s^2).

The interesting thing is that it's actually easier to calculate in the spaceship's reference frame. The two relativistic distortions cancel out and the Newtonian calculation gives the correct answer. So if you accelerate for the first half of your journey it takes you sqrt((28500000040/2)/(365246060*9.81/2)) = 6 years, and the same amount of time to decelerate, meaning 12 years in total.

Re: Seven earth-sized planets discovered circling a star 39 light years from Earth

#320

Post by blueprint »

> The launch cost of launching the mass of the pyramids of gaza into orbit would bankrupt the richest economies.

Yeah… cause the way you're thinking about doing that is literally the only way in the world to accomplish the task. Not. It's not my job to qualify whether it HAS to be done to you. And even though I am the one presenting this information and this evidence, it is indeed your job to confirm it. Otherwise, you're not exactly doing science, are you? Nor are you really acting in your own best interest or that of mankind. It's almost as if you're fighting to rationalize doing nothing. You're free to do that. Just be honest about what you're doing, please. Sacrificing yourself is your choice. But you shouldn't deceive others in order to take them with you.

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