Rig Veda 1.50.8, 1.50.1 O, Bright sun, a chariot named harit with seven horses takes you to sky. Bhagavata Purana also says the same. But Sun cannot physically travel in Chariot.
The bringer of the Sun, Surya was thought to ride his chariot across the sky & defeat the demons of darkness. Sun/Surya may ride his chariot led by seven horses or a single horse with seven heads (representing the colors of the rainbow and seven chakras), all with rays of light shining from them.
The references to Surya's chariot, in a similar manner, can provide us not only information about the ancient Hindus' religious and cosmological beliefs but also about their Science and Astronomical judgements.
Chariot of the Sun-God:
Various scriptures describe the Celestial chariot of the Sun. Rig Veda [1.35] says:
**आ कृष्णेन् रजसा वर्तमानो निवेशयन्न अमृतं मर्त्यं च ।
हिरण्ययेन सविता रथेना देवो याति भुवनानि पश्यन ॥**
Throughout the dusky firmament advancing,
Laying to rest the immortal and the mortal,
Borne in his golden chariot he cometh,
Savitar, God who looks on every creature.
While the Greek Apollo used to ride four-horse chariot, Vedic texts clearly mention Seven horses of Surya who are called - Gayatri, Brhati, Usnik, Jagati, Tristup, Anustup and Pankti. The Rig Veda [1.164.1-5] says:
A seven-named horse draws the three naved wheel,
Seven steeds draw the seven-wheeled chariot,
Wise poets have spun a seven-strand tale,
And glorified this Heavenly calf, the Sun.
Most scholars believe the seven horses represent Seven days of the week. Ancient Indians were great astronomers and this could very well be true. However, I believe, the seven horses probably also represent the Seven colors of Sunlight!
The seven horses of Surya?
Other scriptures talk in a similar vein and describe the chariot of the Sun-god in much detail. Although Arun-deva sits in front of the sun-god and is engaged in driving the chariot, he looks backward toward the sun-god. The chariot has a single wheel with 12 spokes and is yoked to seven horses.
Sixty thousand saintly persons named Valkhilyas, each the size of a thumb, are located in front of the sun-god and offer him prayers. The Gandharvs and Pannags sing in front of him, Apsaras dance before the chariot while Nishachars and Yakshas follow and guard it. These seven groups of fourteen associates arrange the proper times for regular snow, heat and rain throughout the universe and are responsible for maintaining the Seasons on Earth!
Sun moves in chariot with 7 horses means 7 horses are representing the seven colors of Indera danush and Chariot represents the Light Travel in Waves.
Sun is the source of light and that is white light .VIBGYOR ==white Voilet + indigo + blue + green +yellow + orange + red ==white So all 7—horses repersent each colour of the VIBGYOR
As well, Modern physics confirmed that the sun's rays travel in a curved way, but not in a straight line. Our ancestors told that the sun's chariot was drawn by seven horses tied by snakes. As the movements of the snakes are crooked and curved, so also the sun's ray. The phenomenon is described in a metaphysical poetic line bhujagana mita sapta turaga. The chapter on light says that there are seven colors in the white ray of the sun. Artharveda says that there are seven types of sun's rays, sapta surayasya rasmayah.
The Rig Veda repeatedly asks, "How is it that though the Sun is not bound and is directed downwards, it does not fall?" A question asked by Isaac Newton more than three thousand years later, and no one else, because the Greeks had furnished the crystal spheres to which these objects were attached! When we talk of gravity, Newton comes to our mind, but in the text Surya Sidhantha dated around 400 AD, Bhaskaracharya described it stated. "objects fall on the earth due to one force. The Earth, planets, constellations, moon and sun are held in orbit because of that one force".
Note: Puranas explain everything in protective manner (Like Trees and Sun we treat as God), I believe Sun Moves in a Chariot pulled by 7 Horses explains all super natural powers in poetic way to future generations.