The speed of light is the limit with which a material object can move in space, unless, of course, we take into account hypothetical wormholes, with the help of which, according to assumptions, objects can move in space even faster. In an ideal vacuum, a particle of light, a photon, can move at a speed of 299,792 kilometers per second, or about 1.079 billion kilometers per hour. At first glance, it might seem surprisingly fast. No, it's actually fast. But on a cosmic scale, this speed can be excruciatingly slow, especially when it comes to radio communications and flights to other planets, in particular, those outside our solar system.
To make it easier for anyone to understand the limited possibilities of the speed of light, planetary scientist at NASA's Goddard Space Flight Center, James O'Donoghue, created a series of animated videos.
In a conversation with Business Insider, O'Donoghue said that he only recently learned how to make these animations. His first job for NASA was preparing a video about the rings of Saturn. After that, he began to animate other difficult-to-understand space concepts, for example, a visual comparison of the sizes and speeds of rotation of the planets of the solar system. According to him, this work, published on his personal Twitter page, attracted a lot of interest.
His latest work is an attempt to clearly demonstrate how fast and at the same time slow photons can be.
Visual demonstration of the movement of photons around the Earth
In the first animation, O'Donoghue showed how fast light can move relative to the Earth.
Promotional video:
The equator of our planet is approximately 40 thousand kilometers long. If it did not have an atmosphere (the particles it contains can slow down light a little), then a photon sliding along its surface would make almost 7.5 full revolutions in 1 second (or 0.13 seconds per revolution).
While the speed of light appears to be incredibly fast in this scenario, the video also demonstrates that it is finite.
How quickly light travels between the Earth and the Moon
In the second video, O'Donoghue covers a greater distance - from the Earth to the Moon.
On average, the distance between our planet and its natural satellite is 384,000 kilometers. This means that the moonlight seen in the sky travels this distance in 1.255 seconds, and the journey back and forth, for example, when transmitting radio messages between the Earth and spacecraft, will take 2.51 seconds.
It should be noted that this time increases every day, since every year the Moon moves away from the Earth by about 3.8 centimeters (the Moon constantly depletes the energy of the Earth's rotation through gravitational-tidal interaction. The consequences of this effect are a change in the satellite's orbit).
How quickly light travels the distance between Earth and Mars
In the third video, O'Donoghue demonstrated a problem that many planetary scientists have to face on a daily basis.
When employees of the NASA aerospace agency try to download and receive data from a spacecraft, for example, the same InSight probe currently operating on Mars, messages are transmitted at the speed of light. However, it is not enough to control the device in "real time". Therefore, the teams must be carefully thought out, as compressed as possible and directed at the exact time and place so as not to miss the target.
The fastest transmission of messages between Earth and Mars is possible at the moment when the planets are at the point of closest approach. However, this happens only about once every two years. In addition, even in this case, we are separated by a distance of about 54.6 million kilometers. O'Donoghue's video shows that at this distance, light takes 3 minutes and 2 seconds to get from one planet to another, or 6 minutes in both directions.
On average, Earth and Mars are separated by a distance of 254 million kilometers, so on average, two-way message transmission takes about 28 minutes and 12 seconds.
The further the distance, the depressing the "efficiency" of the speed of light becomes
The speed limit of light creates even more problems for spacecraft farther from Earth. For example, the same New Horizons probe, which is now 6.64 billion kilometers from us, or Voyager 1 and Voyager 2, which have reached the edge of the solar system.
Illustration of the Breakthrough Starshot space "nanoprobe" being accelerated by a very powerful laser beam and directed towards the Alpha Centauri star system.
The situation becomes quite sad when it comes to transmitting a message to another star system. For example, the closest exoplanet we know of, Proxima b, is about 4.2 light years away (about 39.7 trillion kilometers). Even if we take the fastest spacecraft at the moment, the Parker Solar Probe, capable of reaching speeds of 343,000 kilometers per hour, then even it would take about 13,211 years just to reach Proxima b.
Nikolay Khizhnyak