Interstellar astronauts would face years-long communication delays due to time dilation

Page 2 - Seeking answers about space? Join the Space community: the premier source of space exploration, innovation, and astronomy news, chronicling (and celebrating) humanity's ongoing expansion across the final frontier.

Classical Motion

Pardon me. I thought entanglement was a certain kind of superposition. A superposition that required locked opposites. Handedness comes to mind. The advantage to this notion is not the state of the superposition, but the presence of superposition. If some one measures the entanglement, that breaks the superposition. If we can detect that breakage, that's all we need. The breakage has to disturb something on the other end. Maybe some of these new sensors might be able to detect it.

Think of putting entangled particles in a media that reacts to particle change.

billslugg

Each particle, on its own, is in a state of superposition between two, sometimes more, possible states. An electron in orbit around a nucleus occupies many locations, or states, at the same time.

Sometimes, two particles in a superposition of states can be created that are entangled. For example, if you take one particle and split it into two particles that happen to have spin, then the conservation of spin rule kick in. You can't have two particles of the same spin or you would be creating spin out of nothingness, which you can't do. They must be opposite spins in order to cancel out. Each one, on its own is in a state of superposition and the two are entangled. When one decides to be spin up the other will instantly assume spin down. No other way to do it.

dgmesser

Well a couple of things, the major one being using 1 g acceleration to near the speed of light.
The amount of fuel, even using a nuclear powered vehicle, with an ISP far greater than we have today, would take an enormous amount of fuel. The mass of which then makes accelerating (and having the nearly same amount of fuel to decelerate as you near your destination) such a mass essentially impossible.
Note, nobody is going to fly to another star system except to land there. There would be no possibility of return.
Which means not only do you need the mass of the landers, but sufficient supplies/equipment to give the people landing on this new world, a chance to survive. The number of people sufficient to start a new colony would also be a major factor. Hard to believe you could do it with less than 100 people.
Considering how long the trip would be, and the mass of people, food, water and power generation, along with the descent stage and materials, the mass of said spacecraft would be huge. Which drives the mass of the propellent required.
Second problem is space is not empty, and at anywhere near the speed of light, no material would withstand the energy imparted from collisions even at space densities.
C/5 might be possible, but even then, going 4 LY would take more than several decades, and you wouldn't be going fast enough for time dilation to reduce the length of the trip.
As to communication, its not just the time it takes for a signal to reach its destination, its the amount of power one would need to send a signal that distance, which for the spacecraft at least would be highly problematical, to have both that much available power and an antenna large enough for the task.
Completely agree with your "reality check" on prolonged 1-g acceleration. The point of the paper is not to deny that relativistic rocket propulsion is a daunting technical challenge, or that energy requirements are not a big challenge. Rather, the paper simply adds to that list of major challenges to be considered (or perhaps to be overcome). The goal is to provide a road map for future research and innovation directed at that goal. Before a bunch of resources are devoted to interstellar travel, all aspects should be considered.

I dont agree with your last point regarding power and antenna size for transmission. The coin of the realm is the product of tx power, tx antenna area, and rec antenna area. Limitations on the tx resources can be compensated by devoting resources to the receiver collector. StarShot, for example, contemplates a km-scale receive collector. Further, any interstellar spaceship must have significant power resources for propulsion and operation that make communication power requirements appear to be a minor add-on.

Classical Motion

It would be interesting to see a list of frequencies.......and a list of distances for the frequencies. For the EM spectrum we detect in space.

I have a feeling(very scientific) that the longest distances are from highly superpositioned sources. Superposition is what gives the intensities required. And this is why we see only certain frequencies at long distance. So physical structures and the number of them, determines what we see. The need for many emitters.

How many light photons would it take to equal one gamma photon? A gamma might have a very less dense flux than light, but show more intensity. So the numbers of structure needed would be less than light. And with gamma, the structures are short lived.

I believe that the condition of superposition controls and sets the long distance frequencies we see here. At long distance.

But it's just a feeling.

This is my definition of superposition. When two or more physical entities occupy the same space at the same time. Only fields can superposition. Mass and particles never can.

Helio

Perhaps the key lies in finding causal behavior for what we see as random events. There could easily be, IMO, wave activity, of some kind, seen only when approaching the Planck scale. Though energy increases with shorter wave lengths, power decreases with amplitude.

Classical Motion

Power is not set with amplitude.......power is set with rate of amplitude. It's a ramp. The steeper the ramp, the more power.

A small amplitude can have great power with rate.

Helio

Power is not set with amplitude.......power is set with rate of amplitude. It's a ramp. The steeper the ramp, the more power.

A small amplitude can have great power with rate.
Do you have a reference!

Here is one showing otherwise…
Here

Classical Motion

That's why those teenie-weenie gammas are so dangerous to bio-matter. Those fast rates can break atomic and molecular bonds. Check out the rate of those bonds. Doesn't take much amplitude to break a protein. An atom buster is not needed for bio-destruction. Molecule damage will suffice.

I don't think living motion and living activities come from physical cause like dead matter does. Living motion is caused by choice. Dead matter has no choice. And no need. It just does. That's why eventually we should be able to discern it. And to start that, we should realize that everything, even thought, is in perpetual motion. Nothing is still. Existence is the state of motion. This state has constant length and constant duration with it. We can change the ratio of them, but not their reference ratios. Those come as one.

The amplitude and the density of flux decreases with distance. But that ramp remains constant with distance. The only thing that can change that ramp........is your velocity. That ramp does not change with emitter velocity.

When the emitter accelerates, the only thing that changes is the duration between the ramps. And this is because of the more length for the next ramp to travel. Light is intermittent ramps. A whole bunch in a flux. White light has many ramp durations.

Nothing is being stretched. The only thing that is stretched is the distance the ramp must travel. The distance for each succeeding ramp is farther. The ramp length remain the same. Unless you are moving.

It's a duty cycle shift. Not a Doppler shift. Only in this case it's a distance cycle shift.

Get it? It's hard for many.

Propagated EM is a duty cycle interaction. A Distance Cycle interaction.

But it's just a feeling I get from what I've read. Pure supposition.

Completely agree with your "reality check" on prolonged 1-g acceleration. The point of the paper is not to deny that relativistic rocket propulsion is a daunting technical challenge, or that energy requirements are not a big challenge. Rather, the paper simply adds to that list of major challenges to be considered (or perhaps to be overcome). The goal is to provide a road map for future research and innovation directed at that goal. Before a bunch of resources are devoted to interstellar travel, all aspects should be considered.

I dont agree with your last point regarding power and antenna size for transmission. The coin of the realm is the product of tx power, tx antenna area, and rec antenna area. Limitations on the tx resources can be compensated by devoting resources to the receiver collector. StarShot, for example, contemplates a km-scale receive collector. Further, any interstellar spaceship must have significant power resources for propulsion and operation that make communication power requirements appear to be a minor add-on.
I agree with your "coin of the realm" comment, but the price one has to pay with that coin increases with the square of the distance.

So for instance, even using huge antennas on Earth, and a decent size antenna on Voyager 1, we are nearing the range we can talk to it, but at 1 LY distance, it would take ~170,000 times the amount of power to do so as it does today at only 157 AU from earth (and 37 min transmission time).
At 2 LY, it would take nearly 30 billion times the amount of power/antenna size, and that's just half the distance to the nearest star.

I think this is interesting to discuss, but for other reasons I mentioned, and dozens I didn't, I don't think humans will ever travel to another star except robotically and that's also highly unlikely as we would never hear from it again.

Classical Motion

We might improve some of those power numbers with lasers. And possibly laser repeaters in orbit of the outer planets. But the basic problem remains. Power with distance.

Maybe we could use length instead. What if we used a line of light....50 miles long? Or even longer? Our optics might be better than our electronics.

Or maybe our electronics could detect a line much easier than a spot.

We might improve some of those power numbers with lasers. And possibly laser repeaters in orbit of the outer planets. But the basic problem remains. Power with distance.

Maybe we could use length instead. What if we used a line of light....50 miles long? Or even longer? Our optics might be better than our electronics.

Or maybe our electronics could detect a line much easier than a spot.
The inverse square law also applies to lasers.
Still there are some aspects which make it better for spacecraft then radio waves, but would not matter at the distances we are discussing.
Consider our current Deep Space Optical Communications experiment, which has transmitted data 10 million miles. Still it required the Palomar Telescope as the receiver and a fairly large laser on the spacecraft.
They hope to do this out to one AU, or ~90 million miles. But a LY is 63,000 AUs. That's the problem when you are faced with the inverse square law.

Replies
42
Views
8K
Replies
27
Views
30K
A
Replies
8
Views
2K
A