5 ways to see Einstein's theory of relativity in real life

The theory of relativity is one of the most famous scientific theories of the 20th century. It is usually thought of as something abstract and not relevant to real life. However, this is not the case at all.

There are several examples of the theory of relativity that we can observe in real life and the technologies we use today. OBOZ.UA has prepared several typical examples of the theory of relativity in action.

Albert Einstein began to formulate the theory of relativity in 1905 to explain the behavior of objects in space and time. It is deceptively simple. First, there is no "absolute" reference frame: whenever you measure an object's speed, momentum, or how it experiences time, it is always related to something else. Second, the speed of light is the same no matter who is measuring it or how fast the person measuring it is moving. Third, nothing can have a speed greater than the speed of light.

GPS navigation

In every smartphone, smartwatch, laptop, and so on, you will find the Global Positioning System function, or more familiarly, GPS. Each satellite carries an atomic clock on board, which runs with an accuracy of one nanosecond.

In order for GPS navigation to work accurately, satellites must take into account relativistic effects. This is because, even though satellites do not move at the speed of light, they still move quite fast. Satellites also send signals to ground stations on Earth. All of these stations (and the GPS technology in your car or smartphone) experience greater accelerations due to gravity than the satellites in orbit.

As the American Physical Society explained to PhysicsCentral, since each satellite is 20,300 kilometers above the Earth and traveling at about 10,000 km/h, there is a relativistic time lag of about 4 microseconds every day. If you add the effect of gravity, the time dilation effect increases to about 7 microseconds (millionths of a second). If these effects were not taken into account, the coordinates calculated from GPS satellites would be wrong within a few minutes. At first glance, this does not sound like a very big difference, but the high accuracy required for GPS requires nanosecond errors, otherwise errors would accumulate at a rate of about 10 km/day. Then the GPS system would be unusable.

Nuclear weapons

Perhaps the most famous "practical consequence" of Einstein's discoveries is the creation of nuclear weapons.

"One of the consequences of the theory of relativity and the model of four-dimensional space that it implies is the statement that all mass is proportional to energy. That is, any particle has a rest energy. Thus, the famous formula E=mc2 explained the mass defect in nuclear decay. In fact, Einstein laid the theoretical foundations for the development of nuclear weapons," said Maksym Vasylenko, a scientist and researcher at the Main Astronomical Observatory of the National Academy of Sciences of Ukraine, in an interview.

However, Einstein was not directly involved in the development of nuclear weapons. He opposed such developments and was even one of the signatories of a letter to President Roosevelt calling for the abolition of nuclear weapons.

Speed radar

If you have ever received a speeding ticket, you can thank Einstein.

Light travels in waves. All waves exhibit the Doppler effect. And this applies not only to emitted waves, but also to those that are reflected from an object, which explains how radar works. Police scanners emit infrared waves that are reflected from cars and then determine the frequency of the reflections when they come back, calculating speed.

Due to Einstein's special theory of relativity and the constant speed of light, radar can make accurate, almost instantaneous, predictions of a car's speed, even if the police car is also moving.

Liquid metal

Why is mercury liquid and has a melting point of minus 39 C°, while gold is solid and has a melting point of 770 C°? Magic? No. The theory of relativity explains it. Mercury is also a heavy atom whose electrons are held close to the nucleus because of their speed, and as a result, we get an increase in mass. The bonds between mercury atoms are weak, so mercury melts at lower temperatures and is usually a liquid when we see it.

An old TV set

Until about the early 2000s, most televisions and monitors had cathode ray tube screens. A cathode ray tube works by firing electrons onto the surface of a phosphor using a large magnet. Each electron creates an illuminated pixel when it hits the back of the screen, and the electrons are ignited, causing the image to move at up to 30% of the speed of light. The relativistic effects are noticeable, so when manufacturers shaped the magnets, they had to take these effects into account.

These principles do not apply to liquid crystal or plasma TVs, as these devices do not rely on electron beams.

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