Within a hundred years, the day on Earth only increased by a few milliseconds. But within the past few decades, science has been able to measure this change with extreme precision.
By using atomic clocks and super-precise measurements of distant quasars (which emit very strong electromagnetic radiation, like a star), we can measure the length of a day at Earth. billionths of a second unit. These measurements are so precise that we can observe various fluctuations like earthquakes in the length of a day.
These fluctuations create challenges and various questions. For a longer period of time, how has the Earth’s rotation changed?
One of the reasons Earth’s days are getting longer and longer is the Moon’s gravitational pull on our oceans.
Tides exert a force on the Earth, gradually slowing its rotation. This process took place over millions of years, making Earth’s days shorter than they are now, so that in the past a year had more days than now.
We know these impacts based on the geological record. It tells us that 620 million years ago, an Earth day was about 22 hours long. However, attempts to measure the length of a day at the present time and in the geologic period are really difficult to make.
Observing a solar eclipse helps scientists measure time. (Photo: Internet).
Hundreds of years ago, no clock was accurate enough to measure this variation. And the fact that the length of a day is fixed to its rotation prevented the researchers from making any comparisons. But recently, science has found a way to study the variation in the length of days on Earth.
Although our ancestors for centuries did not have accurate clocks, they were still brilliant astronomers. They observed and recorded astronomical events such as the Moon obscuring the brightness of stars, as well as solar eclipses. The occurrence of these events is highly dependent on the time and place of the observer.
For example, if an astronomer in one city saw the Moon passing in front of a star one night, an astronomer in a neighboring city would only see the Moon approaching the star without warning. Stop.
By comparing these observations with the actual time of the event, plus calculations from the orbital movements of the Earth and the Moon, we can know the exact time and place of the event. these astronomical events .
Comparing the time taken to make the observations, we get the average rate of increase in time in a day. It has been calculated that, in each century, the day on Earth is about 1.8 milliseconds longer.
There are two interesting things about this result. The first is that researchers are surprised to be able to know this number only through historical documents. Their predecessors made observations spanning more than 2.5 millennia and they were written in different languages as well as observations made in many locations around the world. Collecting them and verifying – is a great effort indeed.
The second thing is that the measured results are lower than the hypothesized results that the researchers put forward, based on the tidal effects of the Moon. This may be due to a change in the overall shape of the Earth.
For example, we know that the melting of ice from the last ice age (about 10,000 years ago) exerted pressure at the Earth’s poles, making it more spherical. This makes the day on Earth a little shorter. The combination of these two effects produced the results we see.
This research work is a great testament to the fact that history can speak to us. If we listen closely, we can even see the change of time .