it’s a SpaceX intern’s idea.

It’s older than that.

https://en.wikipedia.org/wiki/Space_mirror_(climate_engineering)

Space mirrors are satellites that are designed to change the amount of solar radiation that impacts the Earth as a form of climate engineering. The concept was first theorised in 1923 by physicist Hermann Oberth[1][2][3][4] and later developed in the 1980s by other scientists.[5] Space mirrors can be used to increase or decrease the amount of solar energy that reaches a specific point of the earth for various purposes. They have been theorised as a method of solar geoengineering by creating a space sunshade to deflect sunlight and counter global warming.[5][6]

There have been several proposed implementations of the space mirror concept but none have been implemented thus far other than the Znamya project by Russia due to logistical concerns and challenges of deployment.[5][7]

The Znamya project was a series of orbital mirror experiments in the 1990s that intended to beam solar power to Earth by reflecting sunlight. It consisted of three experiments the Znamya 1, Znamya 2 experiment, and the failed Znamya 2.5. The Znamya 1 was a ground experiment that never was launched.[17] The Znamya 2 was the first successful launch the Znamya project had. It was attached to the unmanned Progress M-15.[17]The deployment resulted in a bright light of a width of 5km and with the intensity of a Full Moon being shined.[17] The Znamya 3 was proposed but never acted upon because of the failure of the Znamya 2.5.[17] The project was abandoned by the Russian Federal Space Agency after the failed deployment of the Znamya 2.5.[7]